The invention relates to a filter assembly for high temperature gases, such as the high temperature, high pressure gases discharged from a circulating fluidized bed reactor. It is necessary to treat such gases to remove particles from the gases, and under some circumstances a filtration apparatus for that purpose is desirable. The filtration apparatus typically comprises, such as shown in U.S. Pat. No. 4,869,207 (the disclosure of which is hereby incorporated by reference herein) ceramic tubes. Other known structures include tubular fabric bag filter elements, such as shown in U.S. Pat. No. 4,764,190. While such systems can successfully remove particles from high temperature gas streams, there is a need for such a system that has flexibility in the types of filter elements that can be utilized, and one that is particularly amenable to having a high density of filter surface so that the system can have a minimum size for a given filtering capability.
According to the present invention, a filter assembly for high temperature gases, both from pressurized (i.e. superatmospheric pressure) systems and atmospheric systems, is provided which allows flexibility in the use of the exact filter media, and which can be provided with high density filter surfaces, so as to have a minimum size for a maximum volume. While the invention is useful with conventional candle type ceramic filters (as shown in U.S. Pat. No. 4,869,207), and also may utilize conventional Asahi filters, the invention is particularly useful with CeraMem.RTM. filters such as shown in U.S. Pat. No. 5,114,581. The invention ensures proper filter operation by mounting the filter elements, typically monolithic ceramic cylinders, such as of CeraMem.RTM. material, in apertured plates that are cooled, as by circulating cooling fluid (e.g. water) within them. Also the filters are periodically cleaned by pulsing backflushing gas therethrough, the backflushing of gas known per se for example from U.S. Pat. No. 4,764,190 and co-pending application Ser. No. 07/569,125 filed Aug. 17, 1990, now U.S. Pat. No. 5,242,472. Various hot gas flow directing elements are provided for positively directing the flow of gas, and the filters are arranged in such a manner as to provide optimum filtration for a given amount of volume.
According to one embodiment of the present invention a filter assembly for high temperature gases is provided. The assembly comprises the following elements: A generally upright vessel having a top, a bottom, and a side wall. A high temperature gas inlet adjacent the vessel top. A plurality of filter supporting elements extending generally horizontally within the vessel. A plurality of hollow flow directing elements each defining a generally conical or pyramidal shaped flow directing surface, disposed within the vessel and having a large upper opening, and a smaller bottom opening, each of the flow directing elements terminating in or adjacent a filter supporting element. A plurality of filter elements mounted by each of the filter supporting elements disposed exteriorly of the smaller bottom opening of an associated flow directing element, with the smaller bottom opening of an associated flow directing element extending through its associated filter supporting element. A cleaned gas outlet disposed in the vessel between at least some of the filter supporting elements. And, a particle discharge adjacent the bottom of the vessel.
A gas pulse cleaning means is preferably disposed within the volume between at least some of the filter supporting elements, exteriorly of the flow directing elements, to pulse clean the filter elements. Also there preferably is provided means for directing a cooling fluid into operative association with the filter supporting elements to effect positive cooling thereof. Expansion means may be provided for connecting each flow directing element adjacent a top portion thereof to at least one of the vessel side wall or the filter support element located above it, to allow relative movement between the components so connected. The vessel may be circular in cross-section with the filter support elements circular plate-like elements, and with the flow directing elements thin conical elements having a generally funnel shape.
The filter elements may each comprise a cylindrical monolithic porous material element containing a plurality of passageways extending generally vertically and having a plurality of plugs, and including a microporous membrane applied to the walls of the passageways; that is they may be CeraMem.RTM. material as shown in U.S. Pat. No. 5,114,581 (the disclosure of which is hereby incorporated by reference herein).
The flow directing elements may comprise refractory material bodies having an interior surface formed as the flow directing surface, and the filter supporting elements may comprise rings of heat conductive material having an annular channel therein, the filter elements extending generally vertically and having one end in the annular channel. Alternatively the filter supporting elements may comprise generally planar elements. The openings in the filter support elements may have a progressively smaller cross-sectional area (e.g. diameter) from the gas inlet toward the particle discharge.
According to another aspect of the present invention, a support assembly for a plurality of cylindrical monolithic filter elements is provided. The support assembly comprises the following elements: A support structure having first and second major faces, and means defining a plurality of through extending openings extending from the first major face to the second major face. A plurality of generally cylindrical monolithic filter elements mounted in the through extending openings. And, means for cooling the support structure by circulating cooling liquid into association therewith.
The support structure may be a planar element, or be ring-shaped and have an annular channel formed therein. The radially spaced faces forming the annular channel may be the first and second major faces in which case the cylindrical filter elements will extend generally horizontally, or the major faces may be generally horizontal in which case the filter elements will extend generally vertically.
The invention also has as another embodiment a filter assembly for high temperature gases comprising the following elements: A generally upright vessel having a top, a bottom, and a side wall. A high temperature gas inlet adjacent the vessel top. A plurality of vertically spaced filter supporting elements within the vessel. A plurality of monolithic generally cylindrical ceramic filter elements mounted by each of the filter supporting elements. A plurality of flow directing elements defining flow directing surfaces, disposed within the vessel, for directing the flow of high temperature gases from the gas inlet ultimately toward the filter elements. A cleaned gas outlet disposed in operative association with the vessel between the filter supporting elements, extending through the side wall. And, a particle discharge adjacent the bottom of the vessel.
The flow directing elements may comprise the funnel-shaped elements described above, or vertically staggered non-symmetrical plates disposed on opposite sides of a generally vertical axis of the vessel, the filter supporting elements comprising vertically staggered non-symmetrical elements mounted below each of the flow directing elements. The filter elements may be mounted within a housing including a venturi expander cone disposed between each filter element and the gas outlet, particularly when the filter elements are generally horizontal. Gas pulse cleaning means may be associated with each of the filter elements for directing cleaning gas into the venturi expander cones. The plurality of filter supporting elements may be integral, defining a continuous inner shell substantially concentric with the vessel, or they may be entirely distinct, and each filter supporting element may mount a plurality of vertically spaced rows of filter elements.
It is the primary object of the present invention to provide a desirable filter assembly for treatment of high temperature gases, both pressurized and atmospheric pressure. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.